The invention is a method of hardening transmissions in both directions, particularly between a control station and a transponder, and a device to implement this method. Telecommunications, particularly between a control station and a transponder, for example between a remote control station and a missile, can be jammed either intentionally or unintentionally. Intentional jamming is done by specially designed jamming stations. Unintentional jamming can be caused either by other telecommunications, particularly those using frequencies close to those used for the transmissions in question (for example, communications between other nearby remote control stations and their own missiles) or by various conditions such as hardware failures, interference generated by atmospheric conditions, etc. It is essential to eliminate all the effects of jamming, particularly in missile telecommunications when flight times are relatively short and error-free data exchange is essential.